Synthesis and characterization of perovskite-type BaMg0.33Nb0.67−xFexO3−δ for potential high temperature CO2 sensors application

Abstract

Mixed ionic-electronic conducting BaMg_0.33Nb_0.67−xFe_xO_3−δ was successfully synthesized by conventional solid state method in air at elevated temperature. Fe-doping helped to increase the total conductivity, while the chemical stability under CO₂ at elevated temperatures and under H₂O vapour at boiling conditions decreased with increasing Fe content above x = 0.17 in BaMg_0.33Nb_0.67−xFe_xO_3−δ. Maximum total conductivity of 10⁻³ S cm⁻¹ at 300 °C was obtained for BMNF33 in air, and further increase in Fe content lowered the electrical conductivity, particularly at low temperatures. Activation energy, in the range of 300–700 °C, for total electrical conduction was found to decrease in air by the incorporation of Fe in BaMg_0.33Nb_0.67O₃ (BMN) (BMN: 0.96 eV; BMNF17: 0.72 eV; BMNF33: 0.25 eV). Furthermore, the x = 0.17 composition demonstrated excellent CO₂ sensing characteristics at 700 °C. The investigated perovskite-type metal oxides seem to be promising candidates for monitoring CO₂ (ppm level in air) at elevated temperatures.